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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Experiments and recommendations for the Bentley 50 gearbox, covering synchromesh, centre bearing, and integral sideshaft.

Identifier  ExFiles\Box 112\2\  scan0043
Date  22th October 1937
  
By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}
c. Hs.{Lord Ernest Hives - Chair}
c. Da.{Bernard Day - Chassis Design}
c. Hdy.{William Hardy}

BENTLEY 50 GEARBOX.

Further to Rm{William Robotham - Chief Engineer}/Gry{Shadwell Grylls}12/AP.28.9.37., on this subject, we have now conducted two further experiments to confirm our recommendations.

Non-positive Synchromesh.

On 22.G.V. which has the 3 speed box, we removed the usual synchromesh cam, and changed the plungers for ones of an angle calculated to give twice the end load for no increase in the subsequent friction, of the type designed by Hdy.{William Hardy} for the P.III some time ago. On the bench the measured end load was 96 lbs against the standard 35 lbs. On the road it was impossible to crash the engaging teeth, but the operation was unquestionably too heavy.

We, therefore, reduced the plunger springs to give a load of 67 lbs. It then became possible, if deliberately done, to crash the teeth, but with normal operation this did not happen. A stationary clutch member could be speeded up at 50 m.p.h. in 2nd gear with no trouble. The effort to change gear although heavier than standard if done slowly, was, we consider, satisfactory for Bentley 50, particularly as the Bentley 50 clutch will be 10" or less. Also 9° cones can be used instead of 10°.

Deletion of Centre Bearing.

On B.23.AE we have removed the side shaft centre bearing. No difference in gear noise could be detected.

Integral Sideshaft.

We have asked HHC. to make for test, samples of unground 1st speed straight spur gears. If they can be made quiet enough an integral side shaft will be possible on Bentley 50.

Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}
  
  


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